I have an interesting case where a TSOP56 case S29GL064N (Spansion/ Cypress) was found to have Pin29 left open (not brazed on the PWB).

Pin 29 is "VIO" that powers the I/O buffers of the Flash memory.

The memory has pull-ups (3K32) on signals #BYTE (Pin 53) and I/O buffers (DQ0-DQ15) tied to the 3.3v power supply.

The Memory works fine even with VIO open circuit but found to fail at hot temperature (+85°C).

I Wonder why the Flash is working with the VIO left open and not tied to the 3.3V, except if the I/O buffers could be powered in some way through the pull-ups, and in this case a configuration where the I/Os are not meeting high speed transfer reducing drawn current from the 3.3V by the pull-ups that would maintain the I/Os at correct logic level...

Do you guys have any idea or experience on how the I/O buffers could be powered in my case (pull-ups on I/Os, pull-up on #BYTE, other, ...)?